Interpretation of Surface Marks and Debris Patterns from the 24 May 1973 Union City, Oklahoma Tornado

Abstract

Changes in tornado structure were accompanied by corresponding changes in damage intensity and debris configuration. Initially, damage was light over a 200 m wide path but the vortical nature of the winch was clearly evident. During the mature stage, damage was severe and still showed signs of circulation Intriguing and mysterious microscale patterns were observed in wheat fields. In the shrinking and decaying stages, heavy damage occurred over a 100 m wide path and there was evidence of strong radial inflow in the lowest meter above the surface. Generally, debris was thrown ahead of the vortex, with heavy objects coming to rest on the right forward side. Signs of circulation were no longer apparent in the debris configuration. Flow relative to the moving vortex appeared asymmetrical with strongest winds on the right side of the funnel.